Cloning and molecular characterization of the Fatty Acid Elongase 1 (FAE 1) gene from high and low erucic acid lines of Brassica campestris and Brassica oleracea

摘要

Brassica campestris (sarson) and B. juncea (mustard) are the major sources of edible oils in India. Modification of the Brassica oil for the desired fatty acid profile through genetic manipulation necessitates isolation and characterization of genes involved in the fatty acid biosynthesis. We report the cloning of the Fatty Acid Elongation 1 (FAE 1) genes from two species of Brassica with an objective of characterizing the differences responsible for variation in the erucic acid levels. The product of this gene, beta-ketoacyl-CoA synthase (KCS) is the key enzyme in erucic acid biosynthesis. Consensus primers were used to amplify the target locus from B. campestris, (low and high erucic acid lines), and vegetable B. oleracea. The putative gene from Low and High Erucic Acid B. campestris and lines of B. oleracea were sequenced for further analysis. Proteins of 458 (HEAL Fae 1) and 459 (LEAC Fae 1 and BO Fae 1) were deduced from their respective nucleotide sequences. Clustal analysis revealed a high similarity (98%) at both nucleotide and amino acid sequence level among the clones. Nucleotide sequence similarity of our FAE 1 clones with FAE 1 from Brassica napus was as high as 98%. Likewise, sequence similarities of 86, 84 and 58% were obtained on comparison with FAE 1 from Brassica juncea, Arabidopsis thaliana and Simmondsia chinensis, respectively. The FAE 1 genes from LEAC and HEAC differed at 13 positions at amino acid sequence level. These were mainly localized in the central part of the protein sequence. We propose that the altered amino acid sequence is responsible for low level of erucic acid in LEAC as also speculated by earlier reports. The clones can be used to map the region in Brassica species and engineer plants for modified oil composition.